The rotational speeds (rpm) of spinning rotors of open-end spinning machines have been continuously increased in the past. Over the same time the rpm have been increased, the diameters of the spinning rotors have been reduced.
It has been noted that with the changing of the rotor geometry an optimal yarn formation can only be achieved if the surfaces which come into contact with the fibers fed into the rotor have a different frictional resistance in accordance with their involvement in the yarn-forming process. Specifically, the fiber slide face on which the fibers are fed into the rotor should have a relatively slight roughness, so that the fibers are taken along by the rotor, but still can easily slide into the rotor groove under the centrifugal force of the rotor rotation. In contrast, the rotor groove should have a greater frictional resistance than the fiber slide face, so that the fibers are accelerated to the circumferential velocity by no later than the time the fibers reach the groove.
A spinning rotor is known from German Patent Publication DE 43 05 626 A1, whose fiber slide face and rotor groove have different degrees of roughness and therefore different frictional resistance. This known spinning rotor is initially provided with a nickel-diamond coating in a dispersion bath. In this case the nickel coating provides the appropriate corrosion protection, while the desired roughness and wear resistance is achieved by means of the diamond grains embedded in the nickel coating. In order to provide the different roughness of the fiber slide face and the rotor groove, the spinning rotor is subjected to a mechanical finishing process after coating, i.e. the fiber slide face is separately smoothed.
The processing method following the coating process is elaborate and involves additional process steps. For example, during the polishing process great care must be taken that the rotor groove is not also processed. Following the end of the polishing process it is furthermore necessary to carefully remove the polishing agent as well as the particles removed from the surface, for example by means of a rinsing process.